Overload-release drive connection



March 19, 1940. 1 c. SQHQLL 2,194,327

oyERmApLRELEAsE DRVLVEA c'mmcuon origina; Filed sept. 21, lse 2 sheets-sheet 1 .Mmh 19, 1940.

c. scHoLL OVERLOAD-RELEASE DRIVE'4 CONNECTION Original Filed Sept. 21, 1936 2 Sheets-Sheet 2 Roem/02" f Clar QSC/kol] Patented Mar. `19, 1940 OVERLOAD-RELEASE DRIVE CONNECTION Clark Scholl, Springlield, Ohio, assigner to The Steel Products Engineering Company, Springfield, Ohio, a `corporation of Ohio Original"applicationl September 2.1, 1936,` Serial No. 101,758., Divided and thisapplication May 11, `1938, Serial N0. 207,202 y claims.

The invention relates to overload-releasefdrive connections and more particularly to an improved form of such connection Which is especially adapted for use in a driving mechanism of ascrew 5 conveyer or `othervfuel feeding means of a stoker.

LThepresent application is a'division of my application Serial No. 101,758 led September 21,

It is an object of the present invention `to proclutch which is rugged in construction, capable of transmitting relatively heavy loads `and eco` nomical to manufacture. l

Still another object of the present invention is to provide a device of the type set vforth which is actuated smoothly to disengaged position upon the appliaction of an overload without danger of sticking or sluggishness of action.

Further objects 'and advantages of the inven tion will become apparent as the followingl description proceeds taken in connection with the accompanying drawings, in which:

Figure 1 is a side elevation` of' a portion of a power transmission mechanism provided with an overload-release connection embodying the present invention. l

Fig. 2 is an end 'elevation ofy the overload-release connection shown in Fig, 1. i 1

Figs. 3 and 4 are vertical sectional views of the apparatus of Fig. 1 illustrating the, overload-re- `Vlease connection respectively in its engaged and disengaged positions,

Fig. 5 is a diagrammatic representation of the rmovement of the cooperating latchfand pawl of the overload-release connection. r f

For purposes of illustration of its various novel features, the invention has been shown and described herein as' applied to a power transmission mechanism for a stoker designed particularly for domestic use. The power transmission mechanism partially illustrated herein is of the y'form described and claimed in my copending applica'- n vide an overload-release drive yconnection ory nated generally by the numeral I7, to a cam follower roller I8.- This camfollowerisurged into engagementwith a peripheral cam I9 by a helical tension spring 20, the cam being-journaled on the shaft I I.

Any suitable prime mover, such as an electric motor, may be utilized tol rotate the cam I9. In general, it will be seen that rctation of the cam I9 causes the radius plates I5 to be oscillated sothat the pawl I3 engages successive teeth on the ratchet wheel Ill advancing the same step by step. The resulting step by step movement ofthe driven shaft II may be utilized to move a screw conveyer of a stoker or similar mechanism.

It has heretofore been proposed lto connect certain parts of Stokerv drive mechanisms by frangible' pins so that the connection between thel driving motor and fuel conveyer will be interrupted upon breakage of the pinwhen an over-` load is imposed thereon due" to an obstruction in the conveyer or foranyother reason. Such an arrangement has'the disadvantage, however, that the parts of thev broken pin-must be dislodged and a new pin putin to replace it. This operation may be difficult for an unskilled operator to perform, vespecially if the pin is not located in a readily accessible part of the mechanism. Also, a replacement pin of the proper y frangibility is frequently not available so a nail or any other substitute which comes to hand is used and consequently the driving mechanism together with its primemover aresubjected to the liability of dangerous overloads.

The improved resetting.

In the particular construction illustrated, the overload-release connection II is interposed between a'cam follower yoke or driving memberl 2 I, carrying the cam follower roller I8, and a driven Shaft I I.

follower 2 I'.

member 22, both of which members are rockably *mounted on a shaftv23 parallelingfthe driven As best shownin Fig. 2, the member .'22 is U-s'haped in cross 'section 'as is the` A bifurcated leg 24-on the cam Cam follower'. member 2| extends within the legs of the member 2| and is journaledlon the shaft The overload-release connection preferably includes an arcuate-top .clutch pawl 25 pivotally supported between'the legs 24 by alpin 26 (Fig.

A projection 21 on the clutch pawl 25 is cast inthe oscillatablemember 22.

The clutch 2 pawl 25 is normally'maintained with the projection 21 in contact with the insert 28 by a latch 29, which is pivotally connected to the member 2| by a pin 30. A compression spring 3| mounted within a tubular extension 32 formed on the upper end of the member 22 serves to releasably maintain the latch 29 in contact with the .clutch pawl 25. A suitable adjusting nut`33 is threaded in the upper end of the extension 32 and bears against the upper end of the compression spring 3l so that the compressivey force exerted by the latter may be selectively varied. It will thus be seen that the compression spring 3| normally maintains the latch 29 in engagement wi-thfthe clutch pawl 25 so that the member 22 is rotated in a counterlockwise direction. (as viewed in lig.A 3) upon similar movementl of the cam followerl 2|. In the opposite or clockwise oscillation o the cam follower member 22,l the tensioning.

i follower member 2| is permitted to move relative to it, out of its normal or operative relative position, by the movement of the pawl 25 past the latch 29. In this latter movement the pawl 25 cams the latch 29 upwardly compressing the spring 3|. Accordingly this resistance of the spring 3| to themovement of thepawl 25 prevents such movement until a predetermined overload is exerted on the device. The disengaged position of the overload-release connection or clutch is illustrated in Fig. 4. When in this disengaged position, further rotation of the cam I9 will' not effect any movement of the drive pawl l2 so that the driving mechanism is rendered enltirely inoperative. 'Ihe f compression in the spring 3| may be adjusted by the nut 33 so 'as to vary the load selectively at which the overload clutch release mechanism will trip.

In order to avoid sticking of the release mechanism, due to the increased force exerted by ythe spring 3| as the latch 29 rides upwardly on the pawl 25, the cooperating end surfaces of the pawl and latch are generally rounded and preferably made arcuate in shape, the arcs being tangential andthat on the latch of slightly greater radius than that of the pawl. The pawl and latch move under overload from their normal positions, shown in full lines in Fig. 5, until they occupy the dot-dash line positions'indicated, at the instant of breaking apart. In such case, the pressure angle therebetween increases from a to b and to some extent compensates for the increasing spring pressure. As a result, the release mechanism trips at the selected overload value without substantial variation@ i As apreliminary to the resetting of the overload-release connection, after it has been tripped, the main feed pawl l2 and a backup pawl 311 (Fig. 3) are disengagedv from the ratchet wheel l0 so that the radius plates l5 may be oscillated about the driven shaft in order to bringthe member 22 back into its normal or operative position relative to the cam follower 2|. In this preliminary operation, a shaft 35 carrying .the backup pawl 34, is rotated in a clockwise direction (as viewed in Fig. l) from the position shown in Fig. 5 to that of Fig. 1. One end of the shaft 35 may be squared so that a suitable wrench may be attached to it. The eccentric mounting of the shaft 35 causes it to raise the backup pawl 34 during approximately three-quarters of the clockwise movement of the shaft noted so as to totally or partially relieve the load on the backup pawl. ment of the shaft35, a pin` 36 (Figi 5) in the shaft engages' a shoulder 31 on the hub of the ypawl 34, (Fig. 3) thusturning the pawl completely out of engagement with the teeth of the During the last part of the rotativemoveratchet wheel luf- A detent 38 also connected to the shaft 35 is utilized to lift the main feed pawl yI2 out of engagement with the ratchet wheel. 'This connection includes a tension spring 38 secured to the outer end of the detent 38,

ktheother-end of the spring 'being connected to a pin 4.0 onthe shaft 35 by a chain 4l (Fig. l). As the shaft 35 is turned in a clockwise direction, the outer end of the detent 38 will thusbeliftedv` so that it engages a pin d2 on the main feed pawl |2',"lifting the same out of engagement withL the ratchet wheel lil.

The spring 39 is vinterposed between the shaft 35 and the detent 33 so-that j if the main` feed pawl l2 is contacting a tooth ofthe ratchet'wheel under load, the detent 33 will not raise the main 'feed pawl until the load has beenA relieved by turning the driven shaft H a short distance. desirable because of the light construction oi the detent 38. One end of the'driven shaft ll 'may be squared Yso that it can be readily turned 'by a suitable wrench. l 'v f' This spring arrangement is After this preliminary' disengagement of the pawl and ratchet mechanism, the' overload-release connection or clutch vmay be reset by turn'- ing the shaft 23 in a counterclockwise direction also be squared so that it can be readilyengaged bya suitable wrench'. As the shaft 23 is thus (as viewed in Fig. 4). One end of this shaft may rotated in a counterclockwise direction, 'a ping '43 which extends therethrough (Fig. 2) engagesa complemental notch' Il@ formed on fthe, hub of the member 22 and thus causes themember 22 to move in a counterclockwise direction about the shaft 23 and into operative vposition relative to the cam follower 2|. By the timer that the member22 has been rotated suiciently so that the contacting surface of .the projection 21 on k the clutch pawl 25 can be brought into working position against'the steel inserty 28, a pin ,4555 (Fig.` 3) rigidlymounted on the member 22 en-v gages the rear side of the projection 2'! and turns the clutch pawl 25 thus holding the latch spring v 3| compressed until the upper end of the clutch pawl snaps into place at the forward end of the spring-.pressed latch 29; Since the top'surface of the pawl 25 is radial with respect to the y pivotalk .axis at 26 (see Figs-l, 3` and ll) there is no furtherl compression ofv thespringr during the resetting operation .and-the latter is thus made easy. It will thus be seen .that the overload-release connection maybe readily reset'by a simple manipulation of the apparatus,` More'- over, the resetting operation.is'substantially' instantaneous 'in that a latch need' not beheld .z

in operative position until certain other parts of the apparatus have been vrotated into proper vposition after starting of the prime mover.

After the overload-release connection has been ratchet wheel lll.' The mechanism is` then completely conditioned for'further normal operation. f

While a preferred embodimentl of the device has been illustrated and described, it is contemplated that various changes, alterations or modications may be made Without departing from the spirit and scope of the invention as n expressed in the appended claims.

I claim as my invention:

l. An overload-release drive connection comprising driving and driven members mounted for oscillation about a common axis, a pawl movably secured to one of said members, means including a spring biased overload-released latch for releasably retaining said pawl in position to engage positively the other of said members during oscillations of said driving member in one direction only, and means yieldably urging said driven member in the opposite direction for causing said driven member to follow the return oscillations of said driving member and for alternatively retaining said driven member in an inoperative position at one extremity of its path of movement upon the release of said latch.

2. An overload-release drive connection comprising driving and driven members mounted for oscillation about a common axis, a pawl pivotally mounted on said driving member, an abutment on said drivenmember, means including a springy biased overloadfreleased latch on said driving member releas'ably retaining said -pawl pressed against said abutment for positively connecting said members during oscillations of said drivingl member in one direction only, and means yieldably urging said driven member in the opposite direction for causing said driven member to follow the return oscillations of saiddriving member and for alternatively retaining said driven member in an inoperative position at one extremity of its path of movement upon the release of said latch. ,r

3. An overload-release driveconnection comprising a pair of members mounted for oscillation about a common axis, said members being provided with interengaging portions, means including a spring connected to one of said members for maintaining said interengaging portions in operative engagement kduring oscillation of said members in one direction, and means including a spring pressed latch for releasably maintaining said interengaging portions in operative engagement during oscillation of Said members in the opposite direction. y

4. An overload-release drive connection coniprising, in combination,l a pair of members mounted for oscillation about a common axis, a

clutch VpaWl pivotally mounted on one oi' said oscillatable members and movable into and out of operative engagement with the other vof said `oscillatable members, said pawl being provided with an arcuate bearing surface, and means including a spring urged latch engageable with said paw] and presenting an arcuate bearing surface arranged kto press against that on said -paWl in tangential relation thereto for exerting `pressure on said pawl through a pressure angle f which increases, upon move-ment of said pawl and latch to disengaged position. 5. An overload-release drive connection comn prising, in combination, a pair of members during the resetting of said pawl, whereby substantiallyno increased pressure is placed on said latch spring as said surface rides beneath said i latch during the resetting of the paWl.

CLARK SCHOLL. 

